source: trunk/gsdl3/src/java/org/greenstone/gsdl3/service/ServiceRack.java@ 3851

/*
 *    ServiceRack.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3.service;

// greenstone classes
import org.greenstone.gsdl3.util.*;
import org.greenstone.gsdl3.core.*;

// xml classes
import org.w3c.dom.Node; 
import org.w3c.dom.NodeList; 
import org.w3c.dom.Element; 
import org.w3c.dom.Document; 
import org.xml.sax.InputSource;
import javax.xml.parsers.*;
import org.apache.xpath.XPathAPI;

// general java classes
import java.io.Reader;
import java.io.StringReader;
import java.io.File;
import java.util.HashMap;
import java.util.ResourceBundle;
import java.util.Locale;
import java.lang.reflect.Method;

/**
 * ServiceRack - abstract base class for services
 *
 * A ServiceRack provides one or more Services. 
 * This base class implements the process method.
 *Each service is invoked
 * by a method called process<service name> which takes one parameter - the xml request Element, and returns an XML response Element. 
 * for example, the TextQuery service would be invoked by 
 * processTextQuery(Element request)
 *
 * @author <a href="mailto:[email protected]">Katherine Don</a>
 * @version $Revision: 3851 $
 */
public abstract class ServiceRack
    implements ModuleInterface
{

    /** the absolute address of the site home */
    protected String site_home_ =null;
    /** the name of the cluster (or collection) that this service 
    belongs to - if any */ 
    protected String cluster_name_ = null;

    /** some services can talk back to the message router */
    protected ModuleInterface router_ = null;

    /** a converter class to create Documents etc */
    protected XMLConverter converter_ = null;

    /** the original config info - if need to store it */
    protected Element config_info_ = null;

    /** XML element for describe requests - the container doc */
    protected Document doc_ = null;

    /** XML element for describe requests - list of supported services */
    protected Element short_service_info_ = null;

    /** XML element for describe requests - map of service name to full 
    description */
    protected HashMap service_info_map_ = null;

    /** sets the cluster name */
    public void setClusterName(String cluster_name) {
    cluster_name_ = cluster_name;
    }
    /** sets the collect name */
    public void setCollectionName(String coll_name) {
    setClusterName(coll_name);
    }
    
    /** sets the site home */
    public void setSiteHome(String site_home) {
    site_home_ = site_home;
    }

    /** sets the message router */
    public void setMessageRouter(ModuleInterface m) {
       router_ = m;
    }

    /** the no-args constructor */
    public ServiceRack() {
    converter_ = new XMLConverter();
    doc_ = converter_.newDOM();
    short_service_info_ = doc_.createElement(GSXML.SERVICE_ELEM+GSXML.LIST_MODIFIER);
    service_info_map_ = new HashMap();
    }
    

    /** configure the service module
     *
     * @param info the XML node <serviceRack name="XXX"/> with name equal
     * to the class name (of the subclass)
     *
     * must configure short_service_info_ and service_info_map_
     * @return true if configured ok
     * must be implemented in subclasses
     */
    abstract public boolean configure(Element info); 

    /**
     * Process an XML document - convenience method that uses Strings rather than Elements. just calls process(Element).
     *
     * @param xml_in the Document to process - a string
     * @return the resultant document as a string - contains any error messages
     * @see String
     */
    public String process(String xml_in) {
    
    Document doc = converter_.getDOM(xml_in);
    
    Element res = process(doc.getDocumentElement());
    return converter_.getString(res);
    
    }

    /** process an XML request in DOM form
     *
     * @param xml_in the Element node containing the request
     * should be <message> 
     * @return an Element with the result XML
     * @see Element
     */
    public Element process(Element message) {

    NodeList requests = message.getElementsByTagName(GSXML.REQUEST_ELEM);
    Document mess_doc = message.getOwnerDocument();
    Element mainResult = doc_.createElement(GSXML.MESSAGE_ELEM);
    if (requests.getLength()==0) {
        // no requests
        return mainResult; // empty message for now
    }

    for (int i=0; i<requests.getLength(); i++) {
        Element request = (Element)requests.item(i);
    
        String type = request.getAttribute(GSXML.TYPE_ATT);
        if (type.equals(GSXML.REQUEST_TYPE_DESCRIBE)) {
        Element response = processDescribe(request);
        if (response !=null) {
            mainResult.appendChild(doc_.importNode(response, true));
        }
        
        } else {
        // other type of request, must be processed by the subclass - 
        // send to the service method

        String to = GSPath.getFirstLink(request.getAttribute(GSXML.TO_ATT));        
        Element response = null;
        if (service_info_map_.containsKey(to)) { 
            
            try {
            Class c = this.getClass();
            Class []params = {Class.forName("org.w3c.dom.Element")};
            Method m = c.getDeclaredMethod("process"+to, params);
            Object []args = {request};
            response = (Element)m.invoke(this, args);
            
            } catch (Exception e) {
            System.out.println("ServiceRack: Trying to call a processService type method (process"+to+") on a subclass("+this.getClass().getName()+"), but an exception happened:"+e.toString());
            return null;
            }
            if (response !=null) {
            mainResult.appendChild(doc_.importNode(response, true));
            }
        } else {
            // else error in to field
            System.err.println("ServiceRack describe request: error in 'to' field, non-existant service "+to+" specified!");
            return null;
        }
        }
    } // for each request


    return mainResult;
        
    }

    /** process method for describe requests 
     */
    protected Element processDescribe(Element request) {
    
    Element response = doc_.createElement(GSXML.RESPONSE_ELEM);
    response.setAttribute(GSXML.TYPE_ATT, GSXML.REQUEST_TYPE_DESCRIBE);
    
    String lang = request.getAttribute(GSXML.LANG_ATT);
    String info = request.getAttribute(GSXML.INFO_ATT);
    String to = GSPath.getFirstLink(request.getAttribute(GSXML.TO_ATT));
    
    if (to.equals("")) { // to="", look at info
        if (info.equals(GSXML.SERVICE_ELEM+GSXML.LIST_MODIFIER)) {
        response.appendChild(getServiceList(lang));
        return response;
        } 
        // else error in info field
        System.err.println("ServiceRack describe request: error in 'info' field, info='"+info+"'.");
        return null;
    } 

    // describe a particular service    
    if (service_info_map_.containsKey(to)) {
        response.appendChild(getServiceDescription(to, lang));
        response.setAttribute(GSXML.FROM_ATT, to);
        return response;
    }
    // else error in to field
    System.err.println("ServiceRack describe request: error in 'to' field, to='"+to+"'.");
    return null;
    
    }

    // the following two should be overwritten for info with any language stuff in it
    /** returns the service list for the subclass */
    protected Element getServiceList(String lang) {
    // for now, it is static and there is no lang stuff
    return short_service_info_;
    }

    /** returns a specific service description */
    protected Element getServiceDescription(String service, String lang) {
    Element descript = (Element)((Element)service_info_map_.get(service)).cloneNode(true);
    // for now, create the display element on the fly - look at caching it later
    Element display = createServiceDisplay(service, lang);
    addServiceDisplay(descript, display);
    return descript;
    }
    
    /** adds the display element into the description - appends to the root for now, but may do something fancy later */
    protected boolean addServiceDisplay(Element descript, Element display) {
    if (descript.getOwnerDocument() != display.getOwnerDocument()) {
        display = (Element)descript.getOwnerDocument().importNode(display, true);
    }
    descript.appendChild(display);
    return true;
    }

    /** creates a display element containing all the text strings needed to display the service page, in the language specified */
    abstract protected Element createServiceDisplay(String service, String lang);

    /** overloaded version for no args case */
    protected String getTextString(String key, String lang) {
    return getTextString(key, null, lang);
    }
    /** getTextString - retrieves a language specific text string for the given
key and locale
    */
    protected String getTextString(String key, String[] args,  String lang) {

    String class_name = this.getClass().getName();
    class_name = class_name.substring(class_name.lastIndexOf('.')+1);
    
    Dictionary dict = new Dictionary(class_name, lang);
    String result = dict.get(key, args);
    if (result == null) { // not found
        return "_"+key+"_";
    }
    return result;
    }
}